1. Field of the Invention
This invention relates to a material for the tempering of glass plates, optionally accompanied by their bending, and applies more particularly to the so-called contact-tempering process.
2. Discussion of the Background
It is known from Japanese Patent No. 39-1029 to insert, between the glass and the cooling plates of a contact-tempering device, a material having a mechanical and heat buffering role. The materials proposed include fabric impregnated with silicone oil or grease, i.e. glass cloth which , however, are not satisfactory because they react chemically with the glass (silicone) or are too fragile and are thereby incompatible with an industrial use. A fine and flexible metal sheet, for example, of lead, has been proposed also as another buffering material. In addition to the unsuitability of the heat characteristics of such a metal sheet for the tempering of glass, there is a possible difficulty in precisely applying this metal sheet to cooling plates having complex, nondevelopable shapes.
The inconclusive test of using rovings of metallic threads to contact-temper glass is further mentioned in this prior patent JP 39-1029, since these metallic threads are, on the one hand, difficult to use and, on the other hand, are damaging to the surface of the glass.